It’s a sight Jennifer Schorn, an assistant district attorney in Pennsylvania, will not soon forget: the mobile home of a suspected serial child rapist — allegedly filled with children’s used underwear, explicit photographs and other “trophies” collected over the years — that she toured last week with police.

“It was very late at night when I got the call that I needed to come down and see the trailer first-hand,” says Schorn, a Bucks County ADA, who talked to PEOPLE to offer an inside look at how investigators came to arrest 58-year-old William Charles Thomas.

“This is all so depraved, because the children were so young and he memorialized it,” Schorn claims.

Thomas, a mobile home park handyman, was arrested on Feb. 2 and faces 53 counts in connection with child pornography and a series of sexual assaults beginning in 1997, including five counts of child rape, according to court records obtained by PEOPLE.

At the center of the case against him is the home where he lived — in the mobile home park where he worked — in Bucks County.

Authorities have said they had to remove evidence from his trailer by the truckload and that some of it is from the ’70s. The sheer volume leads them to believe there may be “many, many more victims,” Schorn says.

She says Thomas allegedly sexually assaulted children he got to know at the mobile home park and in a neighborhood in Levittown, Pennsylvania, where he previously lived. Investigators have so far identified five of Thomas’ alleged victims.

“The majority of victims we identified thus far are individuals he came to know when he managed to ingratiate himself into their parents’ lives,” Schorn says. “He apparently comes across as a very nice guy and very helpful — he was a handyman by trade — and slowly gained their trust and then in light of that trust, was able to access their children.”

Thomas has not yet entered a plea and is scheduled to next appear in court on March 15. He will be represented by the public defender’s office, but a specific attorney has not yet been appointed for him.

The mobile home park in Bucks County, Pennsylvania, where William Charles Thomas lived and worked.

Bucks County District Attorney’s Office

‘Layers Upon Layers of Things’ in the Home

Schorn saw inside Thomas’ trailer on Feb. 2, the same day he would be arrested, after police secured a search warrant for his home following a nearly three-month investigation.

When she arrived, she says she couldn’t help but notice the horrified expressions on the faces of police officers she has known for years.

Inside the mobile home, just past the living room, was, according to Bucks County District Attorney Matt Weintraub, Thomas’s alleged “trophy” collection: thousands of items he’s accused of amassing, over decades, in connection with the sexual assaults of children under 10 — mostly little girls, Schorn says.

She says the vast majority of the incriminating evidence was only viewable deeper into Thomas’ home, in an apparent reflection of how he allegedly hid his crimes from public view.

The items she saw included more than 1,000 sexually explicit photographs, drawings and wood carvings, as well as condoms and children’s soiled underwear with “names written in the crotch area.” Police allege that Thomas either kept underwear from his victims as souvenirs or stole it from the homes of residents in which he worked as a handyman.

“There were layers upon layers of things,” Schorn says.

Authorities even found baby dolls he had allegedly altered to feature life-like genitalia, outfitting them with plastic hoses inside, she says.

Police also found a prominently displayed handwritten note near a group of toys and games in one area of Thomas’ trailer specifying the “rules” of the room: that all boys and girls in that space must be naked, according to an affidavit of probable cause obtained by PEOPLE.

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“The most disturbing,” Schorn says, “were the Polaroid images of actual children” — some of whom Thomas had allegedly brought to his trailer, according to the affidavit.

“This is something I wish I never had to see,” Schorn says, “but I am grateful I did so I could accurately describe what was there to a fact-finder — a jury or judge.”

Thomas remains in custody on $750,000 bail, and authorities are asking other potential victims or anyone with information to come forward.

“Our fear is that there could potentially be many more victims,” Schorn explains.

In the course of their investigation, police also found that Thomas had been previously been accused of child abuse in 2000, which child welfare authorities substantiated, according to the affidavit.

While there are no known crimes linked to the evidence that is older than 1997, that could change, a D.A.’s spokesman told PEOPLE last week. The statute of limitations allows prosecution for any identified victims until they turn 50.

A Handwritten Admission?

Police in Falls Township, Pennsylvania, began investigating Thomas in November, according to court records. That’s when the new manager of the Midway Village Trailer Park, where Thomas lived and worked, told police a contractor had found sexually explicit writings on a piece of plywood on their property, Schorn says.

The manager alleged the handwritten notations were from Thomas.

(Midway Village representatives could not be reached for comment. Schorn says the months of investigation before Thomas’ February arrest, following the November accusation, were necessary to establish probable cause.)

According to the affidavit, the plywood writings gave graphic details about “someone sexually assaulting two very young girls,” and the person who wrote it identified the girls by name — providing their physical descriptions and the names of their parents.

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Also listed on the plywood, the affidavit states, was one of the dates and times where this person “first molested a 3-year-old,” along with details of the assault — including a time: early on Dec. 25, 2014.

“It was 1:30 in the morning on Christmas morning and these little girls were probably dreaming of Christmas morning,” Schorn says of the victims. “That probably was one of the hardest things to hear about.”

She says she is now focused on justice.

“We are going to use every possible resource in the continuing investigation and prosecution of this individual to make sure he is never outside of a correctional facility for the rest of his life, because we fear for the safety of the community,” Schorn says.

Anyone with information regarding this case is asked to contact Falls Township police Sgt. Christopher Clark at 215-302-3315 or clarkpd@fallstwp.com or Bucks County detective Lt. Robert Gorman at 215-340-8141 or rmgorman@buckscounty.org.